JOHNSON, CHRISTOPHER A., and ROBERT K. GOLDHAMMER, Exxon Production Research Co., Houston TX

Tectonics and Sedimentation in Northeastern Mexico

The region surrounding the Monterrey salient of the Sierra Madre Oriental fold-thrust belt was examined using Landsat data and field work, in order to determine factors controlling Mesozoic sedimentation and Laramide-age deformation.

Northwest of Monterrey, gentle deformation in the La Popa basin created excellent exposures that chronicle the foreland history of the early phase of Laramide orogenesis. Four sequences of alternating marine and non-marine clastic sediments can be traced laterally over the entire basin using Landsat Thematic Mapper data. These can be linked to eustatic changes in sea level, recorded elsewhere in the northern Gulf of Mexico in latest Cretaceous sediments. Lateral pinchouts, sags, and growth structures in the clastic sediments, associated with salt piercements, were formed during the earliest (Late Cretaceous) phase of local salt destabilization and movement. Thus the massive clastic influx and salt movement were coincident, related to pulses of Laramide uplift farther west and south. S veral times in the Late Cretaceous, during relative sea level highstands, limestone lenses developed on the clastic shelf at topographic highs located above rising salt piercements.

Older basement topography influenced salt distribution, specifically in a prominent north trending Jurassic graben between the Coahuila and Tamaulipas basement highs. Combined with lateral thickness variations in the Upper Jurassic salt, these factors controlled structural development as fold-thrust deformation reached this area of the foreland in Early Tertiary time. During Laramide deformation, thick salt facilitated northward transport of thrust sheets along the axis of the older graben, while the Coahuila basement high acted as a buttress that limited northward progression of deformation west of Saltillo. As the Monterrey salient propagated northward along the rift axis, zones of rotation and shear developed at its western (sinistral) and eastern (dextral) margins.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.